1. Field of the Invention
The present invention relates to a method of producing rubber profiles for windshield wiper blades including a spring elastic supporting strip. The invention relates also to an extrusion head for the production of rubber profiles for windshield wiper blades including a spring elastic supporting strip embedded partly in the heel section of the rubber profile and having rubberfree edge sections extending in its longitudinal extent.
2. Description of the Prior Art
A conventional method of producing windshield wiper blades is an assembling of the supporting strip and the produced rubber profile during a separate tedious manufacturing step.
Furthermore, the rubber lip of the rubber profile which in operation contacts the windshield being wiped must meet high demands: small irregularities of the edges of the lips produce streaks on the windshield. Accordingly, the production of such rubber profiles is a rather intrinsic matter.
In generally known pressing processes such as transfer pressing methods or compression pressing methods the windshield wiper strip profiles are produced in form of double-profiles. Such precursors will be severed longitudinally by means of a punch cutting or by circular knives.
Such severing method produces the edges of the lip of the wiper blade which contact the windshield. Because the cutting is carried out at the product which already has been vulcanized and accordingly has already extremely viscous properties the cutting knives are subjected to a considerable wear. Furthermore, foreign bodies present within the rubber may prevent a clean cut. Due to this reason a separate production step encompassing a cleaning of the rubber mixture is often unvoidable.
Other known methods encompass extrusion processes. In general such processes do not necessitate cutting steps in order to carry out a severing extending in the longitudinal extent of the strips being produced. However, quite often the extruded rubber profile incorporates distortions and accordingly a cutting step for the production of rectilinearly extending edges of the lips is mandatory.